KINETIC-STUDY AT DIFFERENT PH VALUES OF THE OXIDATION PROCESS TO PRODUCE RIPE OLIVES

The kinetics of the oxidation process to produce ripe olives were studied. The sodium hydroxide solutions used for treating the ripe olives contain the same polyphenols as the olives treated with these solutions. These liquids could be utilized as model systems to study the oxidation reactions of polyphenols. However, oxidation of the olive surface was remarkably slower because the diffusion rate of oxygen into the flesh of the fruit was very low. Oxidation of the polyphenols (hydroxytyrosol and caffeic acid) in the sodium hydroxide solutions followed first-order kinetics. The values of the constant for hydroxytyrosol were higher than those for caffeic acid and darkening of the liquids. Olive and solution colour were darker and oxidation rates increased with increasing pH.